This invention relates generally to improved retraction apparatus for automatic feed drills or the like. Particularly, but not by way of limitation, this invention relates to an improved retraction apparatus having means for shifting the feed gear out of engagement with the main drive gear during retraction and to yieldable stop apparatus located in the housing for stopping the retracting movement of the spindle.
In the past, automatic feed drills have been provided with a spring that engages the main drive gear and the feed gear. When the feed gear is released by the feed lever, the feed gear shifts out of engagement with the drive gear and into a position wherein the feed gear is locked. Such an arrangement has been reasonably successful, but in some instances, and particularly when the drill is heavily loaded, there is too much force exerted on the gears to permit the spring to consistently drive the feed gear into its retraction position, that is, into the position wherein it will be stopped. Failure to shift the feed gear can cause the drill to continue to feed, or in some instances, may damage the drill due a stop collar or other device used on the spindle which may engage the drill housing.
Also, various ways have been tried in the past to prevent over retraction of the spindle after the hole has been drilled to the desired depth. In one apparatus, a contact actuated valve is provided that engages a collar or other abutment on the spindle during the retraction movement, shifting the drill into automatic feed movement so that the drill continues to alternate between feed and retraction movement until the operator stops the drill. Also, it has been proposed to provide a stop on the spindle that engages the drill housing causing the drill motor to stall. Manifestly, this has not been very successful in that damage can occur to the various portions of the gear drive mechanism in the drill.
Accordingly, one object of this invention is to provide an improved retraction apparatus for automatic feed drills wherein the drill is positively shifted between the feed and retraction movements, and wherein the retraction movement is stopped in the event that the retraction movement has been completed or in the event that high torque loads are encountered during retraction to prevent damage to the drill.